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Add sections for decltypes and improve descriptions.

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Anthony Calandra
2018-08-23 22:17:56 -04:00
parent 12b9992c01
commit 2f7066a939
3 changed files with 12 additions and 4 deletions
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4
CPP11.md
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@@ -178,7 +178,7 @@ auto f3 = [x] () mutable { x = 2; }; // OK: the lambda can perform any operation
``` ```
### decltype ### decltype
`decltype` is an operator which returns the _declared type_ of an expression passed to it. Examples of `decltype`: `decltype` is an operator which returns the _declared type_ of an expression passed to it. cv-qualifiers and references are maintained if they are part of the expression. Examples of `decltype`:
```c++ ```c++
int a = 1; // `a` is declared as type `int` int a = 1; // `a` is declared as type `int`
decltype(a) b = a; // `decltype(a)` is `int` decltype(a) b = a; // `decltype(a)` is `int`
@@ -197,6 +197,8 @@ auto add(X x, Y y) -> decltype(x + y) {
add(1, 2.0); // `decltype(x + y)` => `decltype(3.0)` => `double` add(1, 2.0); // `decltype(x + y)` => `decltype(3.0)` => `double`
``` ```
See also: `decltype(auto)` (C++14).
### Template aliases ### Template aliases
Semantically similar to using a `typedef` however, template aliases with `using` are easier to read and are compatible with templates. Semantically similar to using a `typedef` however, template aliases with `using` are easier to read and are compatible with templates.
```c++ ```c++

4
CPP14.md
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@@ -89,7 +89,7 @@ int& z = g(y); // reference to `y`
``` ```
### decltype(auto) ### decltype(auto)
The `decltype(auto)` type-specifier also deduces a type like `auto` does. However, it deduces return types while keeping their references or "const-ness", while `auto` will not. The `decltype(auto)` type-specifier also deduces a type like `auto` does. However, it deduces return types while keeping their references and cv-qualifiers, while `auto` will not.
```c++ ```c++
const int x = 0; const int x = 0;
auto x1 = x; // int auto x1 = x; // int
@@ -121,6 +121,8 @@ static_assert(std::is_same<int, decltype(f(x))>::value == 1);
static_assert(std::is_same<const int&, decltype(g(x))>::value == 1); static_assert(std::is_same<const int&, decltype(g(x))>::value == 1);
``` ```
See also: `decltype` (C++11).
### Relaxing constraints on constexpr functions ### Relaxing constraints on constexpr functions
In C++11, `constexpr` function bodies could only contain a very limited set of syntaxes, including (but not limited to): `typedef`s, `using`s, and a single `return` statement. In C++14, the set of allowable syntaxes expands greatly to include the most common syntax such as `if` statements, multiple `return`s, loops, etc. In C++11, `constexpr` function bodies could only contain a very limited set of syntaxes, including (but not limited to): `typedef`s, `using`s, and a single `return` statement. In C++14, the set of allowable syntaxes expands greatly to include the most common syntax such as `if` statements, multiple `return`s, loops, etc.
```c++ ```c++

8
README.md
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@@ -512,7 +512,7 @@ int& z = g(y); // reference to `y`
``` ```
### decltype(auto) ### decltype(auto)
The `decltype(auto)` type-specifier also deduces a type like `auto` does. However, it deduces return types while keeping their references or "const-ness", while `auto` will not. The `decltype(auto)` type-specifier also deduces a type like `auto` does. However, it deduces return types while keeping their references and cv-qualifiers, while `auto` will not.
```c++ ```c++
const int x = 0; const int x = 0;
auto x1 = x; // int auto x1 = x; // int
@@ -544,6 +544,8 @@ static_assert(std::is_same<int, decltype(f(x))>::value == 1);
static_assert(std::is_same<const int&, decltype(g(x))>::value == 1); static_assert(std::is_same<const int&, decltype(g(x))>::value == 1);
``` ```
See also: [`decltype`](#decltype).
### Relaxing constraints on constexpr functions ### Relaxing constraints on constexpr functions
In C++11, `constexpr` function bodies could only contain a very limited set of syntaxes, including (but not limited to): `typedef`s, `using`s, and a single `return` statement. In C++14, the set of allowable syntaxes expands greatly to include the most common syntax such as `if` statements, multiple `return`s, loops, etc. In C++11, `constexpr` function bodies could only contain a very limited set of syntaxes, including (but not limited to): `typedef`s, `using`s, and a single `return` statement. In C++14, the set of allowable syntaxes expands greatly to include the most common syntax such as `if` statements, multiple `return`s, loops, etc.
```c++ ```c++
@@ -743,7 +745,7 @@ auto f3 = [x] () mutable { x = 2; }; // OK: the lambda can perform any operation
``` ```
### decltype ### decltype
`decltype` is an operator which returns the _declared type_ of an expression passed to it. Examples of `decltype`: `decltype` is an operator which returns the _declared type_ of an expression passed to it. cv-qualifiers and references are maintained if they are part of the expression. Examples of `decltype`:
```c++ ```c++
int a = 1; // `a` is declared as type `int` int a = 1; // `a` is declared as type `int`
decltype(a) b = a; // `decltype(a)` is `int` decltype(a) b = a; // `decltype(a)` is `int`
@@ -762,6 +764,8 @@ auto add(X x, Y y) -> decltype(x + y) {
add(1, 2.0); // `decltype(x + y)` => `decltype(3.0)` => `double` add(1, 2.0); // `decltype(x + y)` => `decltype(3.0)` => `double`
``` ```
See also: [`decltype(auto)`](#decltypeauto).
### Template aliases ### Template aliases
Semantically similar to using a `typedef` however, template aliases with `using` are easier to read and are compatible with templates. Semantically similar to using a `typedef` however, template aliases with `using` are easier to read and are compatible with templates.
```c++ ```c++